It is known to feed corrugated paperboard sheets to container blank processing machinery by frictionally engaging an end sheet of a stack of sheets with stationary feed belts, accelerating the belts to accelerate the sheet being fed to the throughput speed of and in register with the downstream machinery, and then shifting the feed belts to an inoperative position out of contact with any sheet until the next end sheet to be fed is similarly engaged. Such sheet feeding apparatus is disclosed in Ward Sr. et al U.S. Pat. No. 4,494,745 (assigned to The Ward Machinery Company) the whole disclosure of which is hereby incorporated herein by reference.
Such sheet feeding apparatus normally feeds one sheet per machine cycle of the downstream container blank processing machinery. It can also be operated in a skip feed mode for feeding longer sheets at half the production rate, that is one longer sheet per two machine cycles. However, with short sheets, even very short sheets, the maximum feeding capability of this feeder is one sheet per machine cycle.
It has previously been recognized that it would be advantageous if sheet feeding apparatus could be developed that could feed from a stack of sheets two smaller corrugated paperboard sheets per machine cycle. An attempt to do this was made by The Ward Machinery Company many years ago. This involved using a kick feed type of sheet feeder (in which a reciprocating kicker engages and positively drives the trailing edge of a sheet) and trying to operate it at twice its normal feed rate to feed two smaller sheets instead of one per machine cycle. Also, to feed one larger sheet per machine cycle, a skip feed mechanism was employed having one or more fingers which raised the stack of sheets above the reciprocating kicker once every other half machine cycle. After trying this out in production on a few container blank processing machines, the modified kick feed was found totally unsatisfactory at double speed production rates. Later, this approach using a double speed kick feeder was tried again in production but again was found unsatisfactory. The conclusion was drawn that this double feed problem could not be solved using a kick feed type sheet feeder, and this approach was abandoned as a failure.
For years the container blank manufacturing industry has waited in need for a sheet feeding apparatus that could successfully and reliably feed two smaller corrugated paperboard sheets per machine cycle of the downstream container blank processing machinery.